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The Daily Vet is a blog featuring veterinarians from all walks of life. Every week they will tackle entertaining, interesting, and sometimes difficult topics in the world of animal medicine – all in the hopes that their unique insights and personal experiences will help you to understand your pets.

Can Your Cat Literally Make You Crazy?

Your doctor warns you that your cat may be a risk to your unborn child. Her concern is a parasite common to cats called Toxoplasma gondii. Cats shed this parasite in their feces or poop. Pregnant women infected with Toxoplasma can transfer the infection across the placenta to the baby. Once infected, the infant can suffer irreversible damage to the brain and retinas of the eye. The infants can also be born with malformations of the nose.

That is why the doctor asks dad to take over litter box duties and tells mom to wash her hands after petting the cat and avoid having the cat lick her face.

The doctor may have forgotten to make sure mom wears gloves when working in the garden and washes her hands thoroughly after handling raw vegetables and meats. She may have also forgotten to tell mom to avoid eating raw or undercooked meats, raw milk and unwashed vegetables. Infection from food is much more common than infection from the cat.

But unborn babies are not the only ones at risk. And infection with T. gondii in adults is now being linked to the mental disorder schizophrenia. Dr. Gary Smith at the University of Pennsylvania’s School of Veterinary Medicine just published a study that suggests that one-fifth of people with schizophrenia involve toxoplasma infection. Other researchers have also linked attention deficit hyperactivity disorder (ADHD), obsessive compulsive disorder, and suicidal behavior to infections with T. gondii.

What is Toxoplasma gondii?

Toxoplasma gondii is a single celled parasite that can infect all warm-blooded animals. In fact, it is estimated that 1/5 of Americans and 1/3 of all humans are infected with T. gondii. The cat family (both domestic and wild) is the definitive host for the parasite. T. gondii sexually reproduce in the intestines of the cat producing millions of oocysts (infectious “seeds”) that are shed in the feces and into the environment. The oocysts are very tough and can survive for long periods of time, even under harsh circumstances. Other animals and humans are infected by direct contact with the feces (eating the feces or eating after handling the feces without washing the hands). Eating unwashed products that are grown in contaminated soil, like vegetables, is another method of direct ingestion of the oocysts.

Once eaten by another animal, the oocysts multiply in the body and invade muscle, organs, and the brain and become permanent cysts. These cysts are infectious, so eating raw or undercooked meat with T. gondii cysts is the most common method of infection. It can also be shed in the milk of infected animals.

What Are the Symptoms of T. gondii Infection?

Most humans infected with T. gondii have no symptoms of infection. Mild flu-like symptoms occur in some people. Some adults develop permanent damage to the retina of the eye, but generally infection in adults does not cause illness. Infants, HIV/AIDS patients, or others with weakened immunity can become very ill, sometimes fatally.

This new study, like previous studies, suggests that maybe most infections with T. gondii are not uneventful and cysts in the brain can affect behavior. But hopefully it won’t revive the old notion of the “Crazy Cat Lady Syndrome.” Early researchers suggested that compulsive cat hoarding behavior was from infections of T. gondii that these individuals got from the cats they kept.

The high, worldwide infection rates of T. gondii are not from cats. Cats only shed oocysts in their feces for a few weeks after infection. The biggest route of infection is from food.

How to Avoid Infection from Toxoplasma

During the time I owned my cat-only hospital, I was called by a physician who wanted me to put his patient’s cat on permanent antibiotics for toxoplasmosis infection. His patient had advanced AIDS and he didn’t want to take any chances of the cat giving the owner toxoplasma. I told the physician that I had tested the cat’s feces and blood for evidence of toxoplasmosis and felt the cat was free of the condition. I told him I was not going to put my patient on medication that was not needed and it was inappropriate for him to ask that of another professional. He went on about how I was risking the health of the cat’s owner.

I asked him is he had instructed his patient to wash his hands thoroughly after handling raw vegetables and meats. He answered, “Should I?” I then asked if he cautioned his patient about eating raw or undercooked meat or raw milk. He again asked, “Should I?” I asked whether he told his client to wear gloves and take precautions when gardening. Finally I asked whether he had discouraged his patient from partaking in potluck dinners where he might not know how the food was handled or prepared. To both questions, he replied the same: “Should I?”

I finally said “Yes, you should” and asked why he didn’t know more about the transmission of diseases he treated. I explained that food, food preparation and poor hygiene were a much greater threat to his patient. I refused to put my patient on antibiotics it didn’t need.

Your cat may drive you crazy, but it is unlikely to make you crazy. Food and food handling is a bigger threat to your mental health.